This invention relates to a process for a self-healing metallized film capacitor in which the metallization material is so chosen to provide both a desired sheet resistivity and a given metallized electrode thickness. The invention relates to a process for making metallized film capacitors in which electrode thickness and clearability (self-healing characteristics) are important considerations, e.g., capacitors subjected to high electrical stress.
Prior art teaches that improved self-healing of metallized film capacitors can be obtained by decreasing the thickness of the metallized layer. However, decreasing the electrode thickness decreases the quality of end connection, increases the edge field, increases the difficulty in controlling electrode thickness and, in the case of an AC capacitor, increases the rate of electrode loss due to corrosion.
It has been proposed to use an aluminum-copper alloy metallization to reduce capacitance loss in metallized film capacitors. However, with this alloy, it was felt necessary to reduce metallization thickness to improve the self-healing characteristics.
Aluminum-copper alloy metallization in normal thicknesses has been used in self-healing capacitors but at a high copper content.